Modular trial mechanism

ABSTRACT

A prosthetic trial for a joint prosthesis includes a stem having a proximal section and a distal section for implantation in a bone. A body includes a channel receiving at least the proximal section of the stem. A locking mechanism is at least partially disposed within the body. The locking mechanism is biased into a locking position in which the mechanism locks the stem within the first channel of the body. The locking mechanism is accessible outside said body to be pulled into a releasing position to unlock the stem from the body.

This application is a continuation of application Ser. No. 10/260,137,filed on Sep. 30, 2002, which issued on Sep. 25, 2007 as U.S. Pat. No.7,273,499, the disclosure of which is herein totally incorporated byreference in its entirety.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to a surgical trial instrumentassembly and, more particularly, to a surgical trial instrument assemblyfor determining the required dimensions of a prosthetic femoralcomponent.

BACKGROUND OF THE INVENTION

During the lifetime of a patient, it may be necessary to perform a jointreplacement procedure or anthroplasty on the patient as a result of, forexample, disease or trauma. One such type of joint replacement procedureis a hip replacement procedure in which a diseased and/or damaged hipjoint is replaced with a prosthetic hip joint. A typical hip replacementprocedure utilizes a prosthesis that generally includes a femoral stemcomponent, a proximal body component, and a neck segment. The femoralstem is implanted in a prepared medullary canal of the patient's femur.

During performance of such a hip replacement procedure, the surgeon mustevaluate the size and condition of the patient's bones (e.g. thepatient's femur) in order to determine the proper type and configurationof each of the various types of prosthetic components that are to beimplanted. One or more provisional components are temporarily fixed to abone prior to permanent fixation of the prosthetic joint. Theprovisional components are intended to mimic certain aspects of thepermanent prosthetic joint in order for a surgeon to validatemeasurements and to test several different possible component sizes andshapes. Hence, provisional components are aptly known as “trials”, andthe procedure is known as “trialing.”

Currently, in a majority of revision total hip arthroplasties, the bonehas little or no supportive metaphysis or diaphyseal areas. This makesit difficult for surgeons to reproduce the proper anatomy. To do this,the surgeon may use a distally fixed implant. This facilitates trialingfrom the distal femoral cortex and subsequent proximal anatomy. Manytrials are used in surgery having one basic anterior/posterior proximalanatomical body with altering characteristics (i.e., stem lengths, bow,offsets, neck lengths, neck anteversion). Each instance requires asingle monolithic trial that duplicates the implant, which is thereinmade from casting substrate.

Other modular devices contain modular similarities but may not addressmulti-functional characteristics as per using both neck segments anddistal stem variations simultaneously. They also may not usepre-existing broach system neck segments and its instrumentationtechnology to simplify case sizing.

Other techniques require that the broach be removed from the medullarycanal to allow the use of a trial having a stem portion, a head and aneck. For example, U.S. Pat. No. 5,100,407 discloses a system includinga group of variously sized trial neck/body portions and a group ofdiffering length trial stem portions which are mixed and matched tocreate a suitable trial. However, repetitive removal and insertion ofsuccessions of trial stems accompanied by successive assembly anddisassembly with respect to the body can require more time, which willincrease operating room cost.

Another known trial includes a stem to which a collar is secured atsuccessive points along the length of the trial until an appropriateneck length and stem length have been ascertained. Undesirably, thistype of trial induces measurement inaccuracies resulting from stemmovement as the collar is repeatedly engaged and disengaged from thestem. Additionally, as the collar is moved toward the distal end of thestem, less of the stem is disposed within the medullary canal, causingthe trial to become increasingly unstable and rendering accuratemeasurements difficult to achieve.

Any additional anatomical complexity can increase the undesirablenumbers of trial components in a kit. For example, trials for long hipstems must be different for the right and left femur due to thecurvature or bow of the respective femurs. In other words, a long leftstem trial cannot be used in the right femur and vice versa. It isbelieved that a trial system consisting of numerous parts that must beselected and mated in various combinations, possibly many times, iscumbersome.

Another example, U.S. Pat. No. 6,193,759, uses two component embodimentsbut has not included an additional neck segment component thatencompasses different geometries. The '759 patent does not address theability to be used on one single broaching system. The system of the'759 patent also does not used the same instrument system to implant orextract both the broach and trial.

Because many variations in sizes and shapes of trials are required to beavailable to the surgeon, it is necessary to maintain a large inventoryof trials and/or trial components. Such a large inventory is costly,occupies valuable operating room space, and is difficult to manage.Another problem is that if a trial is to be assembled from multiplecomponents, the assembly and disassembly of the trial can consume largeperiods of operating room time.

What is needed therefore is a femur implant trial that can be quicklyand easily assembled and disassembled from multiple components.

What is further needed therefore is an apparatus and method forassembling various sizes and shapes of trials from a minimum number ofcomponents to be kept in inventory.

SUMMARY OF THE INVENTION

The present invention provides a modular trial assembly that can beassembled, with a minimum inventory of trial components, to mimic manydifferent variations of prosthetic sizes and shapes. The modular trialassembly can be quickly and easily assembled from the trial components.

The present invention reduces the amount of trial sizes by using oneproximal body and varying neck and stem component geometry. It alsopotentially reduces production cost by being made of lower gradestainless steel. The present invention also potentially reduces thesterilization case weight. The trial system of the present invention canbe aligned and removed by the same extraction instrument used on thesubsequent broaching system, simplifying the overall system. The trialsystem also uses neck segments used on a subsequent broaching systemthat has different styles of proximal head configurations.

The prosthetic trial of the present invention includes a proximal bodyportion that engages the distal stem portion, allowing for differentlengths of stem geometry. A single distal stem portion can be curved andreversibly secured to the proximal body portion to provide a long stemtrial suitable for either the right or left femur.

In accordance with one embodiment of the present invention, there isprovided a prosthetic trial for a joint prosthesis. The trial includes astem having a proximal section and a distal section for implantation ina bore. A body includes a channel receiving at least the proximalsection of the stem. A locking mechanism is at least partially disposedwithin the body. The locking mechanism is biased into a locking positionin which the mechanism locks the stem within the first channel of thebody. The locking mechanism is accessible outside said body to be pulledinto a releasing position to unlock the stem from the body.

In accordance with another embodiment of the present invention, there isprovided a prosthetic trial for a joint prosthesis. The trial includes aneck having one of a first projection and a first recess. The neck alsohas one of a second projection and a second recess. A body assemblyincludes the other of the first projection and the first recess. Theother of the first projection and the first recess is coupled to the oneof a first projection and a first recess. The body assembly alsoincludes another of the second projection and the second recess. Theother of the second projection and the second recess is coupled to theone of a second projection and a second recess such that the neck andthe body are nonrotatable relative to each other. A stem is detachablyconnected to the body assembly.

In accordance with yet another embodiment of the present invention,there is provided a prosthetic trial for a joint prosthesis. The trialincludes a body, a stem separate from the body, a neck separate from thebody and the stem, and a locking mechanism at least partially disposedwithin the body. The locking mechanism locks the stem to the body andunattachably couples the neck to the body.

An advantage of the present invention is that many variations of sizesand shapes of trials can be assembled from a small number of trialcomponents that are kept in inventory.

Another advantage is that a trial can be quickly and easily assembledfrom trial components, thereby saving operating room time.

The above and other features and advantages of the present inventionwill become apparent from the following description and the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded, partially sectional, perspective view of oneembodiment of a modular trial assembly incorporating features inaccordance with the principles of the present invention;

FIG. 2 is a front view of one embodiment of a modular trial assembly kitfrom which the modular trial assembly of FIG. 1 can be assembled inaccordance with the principles of the present invention;

FIG. 3 is a perspective, partially sectional, fragmentary view of themodular trial assembly of FIG. 1 in an assembled state;

FIG. 4 is another exploded, partially sectional, perspective view of themodular trial assembly of FIG. 1;

FIG. 5 is a front, partially sectional, fragmentary view of the modulartrial assembly of FIG. 1 in an assembled state;

FIG. 6 is a side view of the body and stem of FIG. 1 in an assembledstate;

FIG. 7 is an enlarged, fragmentary, side view of the body and stem ofFIG. 1 in an assembled state;

FIG. 8 is a front, partially sectional view of the modular trialassembly of FIG. 1 in an assembled state;

FIG. 9 is a front view of the prosthesis for which the assembled modulartrial assembly of FIG. 8 trials;

FIG. 10 is a front, partially sectional, fragmentary view of oneembodiment of a handling tool used to place and/or extract the assembledcombination of the body and stem of FIG. 1;

FIG. 11 is a plan, fragmentary view of the handling tool of FIG. 10;

FIG. 12 is a front view of a broach that can be used with the handlingtool of FIG. 10;

FIG. 13 is a top view of the broach of FIG. 12 along line 13-13.

FIG. 14 is a perspective, partially sectional, fragmentary view ofanother embodiment of a body and a stem, and an unlocking tool of thepresent invention;

FIG. 15 is a front, sectional, fragmentary view of the body and stem ofFIG. 14 in an assembled state;

FIG. 16 is an enlarged view of the proximal ends of the body and stem ofFIG. 14 in an assembled state;

FIG. 17 is a front, sectional, fragmentary view of another embodiment ofa body and a stem in an assembled state;

FIG. 18 is a front, fragmentary view of the body and stem of FIG. 17;and

FIG. 19 is a side, fragmentary view of the body and stem of FIG. 18along line 19-19;

DETAILED DESCRIPTION OF THE INVENTION

While the invention is susceptible to various modifications andalternative forms, a specific embodiment thereof has been shown by wayof example in the drawings and will herein be described in detail. Itshould be understood, however, that there is no intent to limit theinvention to the particular form disclosed, but on the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by theappended claims.

It should initially be appreciated that the present invention can beused after proper resection of a patient's proximal femur for evaluatingthe size and shape of an implant therefor prior to committing to thefinal preparation of the proximal femur. The proximal end portion of thepatient's femur can be resected by use of, for example, a bone saw (notshown). Proper resection of the proximal femur is beyond the scope ofthe present disclosure. Reference should be made to an appropriatesurgical manual for such resection.

Referring now to FIG. 1, there is shown a modular trial assembly 20according to one embodiment of the invention, including a distal stem22, a main body 24, a plunger 26, a coil spring 28, a stud 30 and a necksegment 32. The stem 22 is separate from the body 24, and the neck 32 isseparate from the body 24 and the stem 22. The plunger 26, the coilspring 28 and the stud 30 together form a locking mechanism. The body 24and the locking mechanism together form a body assembly. The trialassembly 20 can preferably be made of stainless steel. However, it ispossible to form the trial assembly 20 of other materials, such astitanium, cobalt, etc.

As shown in FIG. 2, a trial system kit 34 can include multiple sizes ofeach of the distal stem 22, the main body 24 and the neck segment 32.More particularly, the kit 34 can include a small neck 32 a, a largeneck 32 b, a small body 24 a, a large body 24 b, two small stems 22 a,22 b, and a large stem 22 c. The kit 34 can also include multiple shapesof the stem 22. For instance, the stem 22 a is straight while the stems22 b and 22 c are bowed. Thus, different sizes and shapes of the stem22, the body 24 and the neck 32 can be mixed and matched with oneanother to produce a modular trial assembly 20 that matches the size andshape of the patient's joint anatomy. Various trial assemblies may betried in order to ascertain which final implant will work best, in thesurgeon's judgment. Regardless of which combination of necks 32, bodies24 and stems 22 is used to assemble the modular trial assembly 20, themanner of assembly, which will be discussed in detail herein, issubstantially the same.

Returning to FIG. 1, the stem 22 includes a distal section 36 and acylindrical proximal section 38. The distal section 36 is configured forimplantation in a bore of a femur. The distal section 36 has a size andshape that is substantially the same as that of the implant for whichthe distal section 36 trials.

The proximal section 38 includes a key element in the form of a tang 40,an annular groove 42, and two opposing recesses in the form of slots 44.Each slot 44 has a cross section with two right angles, as shown in FIG.2. However, it is also possible for the slots 44 to have variouscross-sectional shapes, such as V-shaped, U-shaped, etc. Each slot 44 isoriented generally perpendicular to the tang 40. An upper side 45 of theslot 44 is oriented at an angle of approximately 45° relative to thelongitudinal axis of the stem 22. The proximal section 38 has a diameterthan is less than the diameter of the distal section 36, thereby formingan annular shoulder 46 at their junction. Two stem anatomical referencesin the form of inscriptions 47 are provided on the outer surface of theproximal section 38, with one inscription 47 being below each of slots44. Each of the inscriptions 47 can identify the stem 22 as being one ofstems 22 a, 22 b and 22 c, i.e., identifies the size and shape of thestem 22.

The body 24 includes two intersecting through channels 48 and 50oriented at an angle of approximately 45° relative to each other. Thechannel 48 has a rectangular opening 52, best seen in FIG. 3, at aproximal end 54 of the body 24. The channel 48 also has a distal opening56 at a distal end 58 of the body 24. The channel 48 is sized to receivethe proximal section 38 of the stem 22. The proximal opening 52 isconfigured to receive the tang 40 of the stem 22.

The channel 50 is oriented parallel to the longitudinal axis of the neck32. The channel 50 has an opening 60, best seen in FIG. 4, at a medialside 62 of the body 24. The medial side 62 is oriented at an angle of45° relative to the channel 48 and is oriented perpendicular to thechannel 50. This orientation allows the medial side 62 to interface withthe neck 32. An annular shoulder 63 disposed in the channel 48 at themedial side 62 of the body 24, and best seen in FIG. 5, defines theopening 60. In one aspect of the invention, the diameter of the opening60 is smaller than the diameter of the channel 50. The channel 50 alsoforms an opening 64, best seen in FIGS. 6 and 7, at a lateral side 66 ofthe body 24. The opening 64 is generally oval because the channel 50intersects the lateral side 66 at an angle.

The medial side 62 of the body 24 defines an L-shaped slot 68 adjacentthe proximal end 54 and extending from an anterior side 70 to aposterior side 72 of the body 24. As shown in FIGS. 3 and 4, the slot 68is generally perpendicular to the plane defined by the channels 48 and50. The proximal end 54 of the body 24 also includes a linear slot 74.The slot 74 includes and is an extension of the opening 52 of thechannel 48. The slot 74 extends from the lateral side 66 toward themedial side 62 of the body 24, parallel to the plane defined by thechannels 48 and 50. The slot 74 is in communication with the channel 48in order to receive the tang 40 of the stem 22. The slot 74 is also incommunication with the L-shaped slot 68 in order for the slot 74 toreceive a portion of the neck, as will be discussed in more detailbelow.

The lateral side 66 of the body 24 includes an arcuate slot 76 (FIG. 7)extending from the anterior side 70 to the posterior side 72 of the body24, perpendicular to the channel 48. The arcuate slot 76 is incommunication with both the linear slot 74 and the channel 48 in orderto provide access to the stem 22 when the stem 22 is inserted into thebody 24, as will be discussed below.

Looking now at FIGS. 1 and 4, the plunger 26 includes a projection inthe form of a pin 78 extending from a head 80. The pin 78 is forinsertion into a selected one of the slots 44 of the stem 22. A shaft 82having exterior threads 84 extends from an opposite side of the head 80.The plunger 26 is sized to fit within the channel 50.

The spring 28 has a diameter greater than the diameter of the shaft 82but less than the diameter of the head 80. Further, the diameter of thespring 28 is greater than the diameter of the opening 60, and thediameter of the shaft 82 is less than the diameter of the opening 60.Thus, the shaft 82 will pass through the opening 60, but the spring 28and the head 80 will not pass through the opening 60.

The stud 30 includes a lateral end 86 having a recess 88 with interiorthreads 90. The outer diameter of the lateral end 86 is greater than thediameter of the opening 60. The threads 90 have a size and spacing thatallow the threads 90 to receive the threads 84 of the plunger 26. Theouter surface of the stud 30 can include an annular groove 92 to allowan assembler to obtain a firm grip on the stud 30.

The neck segment 32 includes a cylindrical cavity 94 in a lateralsurface 96. The cavity 94 is sized to receive the stud 30 therein. Theneck segment 32 also includes a block-shaped projection 98 (see FIGS. 1and 5) extending from the surface 96. Another projection in the form ofa fin 100 is disposed partially on an upper surface of the projection 98and partially on a top surface 102 of the neck segment 32. The fin 100is oriented parallel to the cavity 94. The projection 98 and the fin 100are for insertion into the L-shaped slot 68 and the linear slot 74,respectively, to couple the neck 32 to the body 24.

During assembly, the spring 28 is inserted through the opening 64 andinto the channel 50. The plunger 26 is then also inserted, threaded endfirst, through the opening 64 until the threads 84 pass through thespring 28 and through the opening 60. The stud 30 is placed at theposition shown in FIG. 1, on the medial side of the opening 60. The stud30 is then coupled to the plunger 26 by virtue of their mating threads90 and 84, respectively. Thus, the stud 30 is accessible outside of thebody 24.

Once the plunger 26 has been screwed into the stud 30, the surgeon ortechnician can manually grasp the stud 30 around the groove 92 and pullthe stud 30 in a medial direction, as indicated by arrow 104 in FIG. 4.The attached plunger 26 is also pulled in the direction 104 against thebias of the spring 28. As the plunger 26 moves, the head 80 of theplunger 26 compresses the spring 28 against the shoulder 63 on which thespring 28 is seated. The stud 30 is pulled in direction 104 until theplunger 26, including the pin 78, has passed through and is disposedinboard and clear of the channel 48. At this point, the lockingmechanism is in a releasing position.

The stem 22, and particularly the portion 38, is then inserted into thechannel 48 through the distal opening 56. The stud 30 is heldstationary, keeping the plunger 26 out of the channel 48, while the tang40 and the groove 42 of the proximal section 38 pass by the channel 50.Once the tang 40 has arrived at the proximal opening 52 of the channel48, the stem 22 is rotated if necessary so that the tang 40 is alignedwith and can be inserted into the linear slot 74 at the proximal end 54of the body 24. One of the inscriptions 47 is visible through theopening 64 when the tang 40 is aligned with and near the slot 74. Thus,the surgeon or technician can look for the inscription 47 through theopening 64 to determine if the tang is properly aligned with the slot74.

If one of the bowed stems 22 b or 22 c is being inserted, it must beverified that the bow is oriented in the desired direction before thetang 40 is inserted into the slot 74. If the tang 40 is inserted intothe slot 74 with the bow in the wrong direction, the tang 40 must bewithdrawn from the slot 74 and the stem rotated 180° before the tang 40is reinserted into the slot 74. With the tang 40 in the slot 74, thestem 22 is prevented from rotating in the channel 48.

The stud 30 can be released and the lateral end 86 of the stud 30becomes seated on the shoulder 63. The bias of the spring 28 pushes theplunger 26 in a lateral direction, opposite to the direction 104, untilthe pin 78 of the plunger 26 is seated in a slot 44 of the stem 22. Thepin 78 thus locks, attaches or detachably connects the stem 22 withinthe body 24. The locking mechanism is now in a locking position.

At this point, the groove 42 of the stem 22 is aligned with the slot 76of the body 24, as best seen in FIG. 5. In addition, the inscription 47is also visible through the opening 64, as best seen in FIG. 7. Thus,which of the stems 22 a, 22 b and 22 c is locked to the body 24 can beeasily discerned by looking at the inscription 47 through the opening64. The shoulder 46 of the stem 22 is closely adjacent to, and ispreferably in contact with, the distal end 58 of the body 24, as bestseen in FIG. 6. The diameter of the stem 22 at the shoulder 46 is equalto the diameter of the end 58, thereby forming a seamless junctiontherebetween, which best mimics the smooth surface of the prosthesis forwhich the assembly 20 trials.

The neck segment 32 is then placed on and unattachedly coupled to thebody 24. What is meant herein by “unattachedly coupled” is that the necksegment 32 is coupled to but not attached to the body 24. For example, asingle linear force, such as gravity, exerted on either the neck segment32 or the body 24, while the other of the neck segment 32 and the body24 is held stationary, can separate the neck segment 32 from the body24.

In order to unattachedly couple the neck segment 32 to the body, thecavity 94 of the neck 32 is aligned with the stud 30, and the stud 30 ispartially inserted into the cavity 94. The fin 100 of the neck 32 isaligned with the linear slot 74 of the body 24, and the neck 32 is fullypressed onto the body 24. The fin 100 is received in the slot 74, theblock-shaped projection 98 is received in the L-shaped slot 68, and thestud 30 is fully received within the cavity 94. With the fin 100 in theslot 74, the neck 32 is prevented from rotating relative to the body 24.The block-shaped projection 98 in the slot 68 prevents the neck 32 frommoving in the directions of double arrow 105 in FIG. 5, thereby reducingforce exerted on the stud 30 in directions 105 by the neck 32.

The neck 32 is shown as including projections 98, 100 received inrecesses 68, 74 on the body 24. However, in another embodiment (notshown), one or both of the projections 98,100 of the neck are replacedby a respective recess, and one or both of the recesses 68, 74 of thebody are replaced by a respective projection received in thecorresponding recess of the neck. In general, whether one or both of theprojections are placed on the neck or are placed on the body isarbitrary. So long as there are at least two projections andcorresponding recesses on the neck and body, the neck and body will notbe able to rotate relative to each other, and the neck can beunattachedly coupled to the body.

At this point, the modular trial assembly 20 is fully assembled, asshown in FIG. 8. An implant 106, for which the assembly 20 trials, isshown in FIG. 9. As can be seen in a comparison of FIGS. 8 and 9, theassembly 20 closely mimics the size and shape of the implant 106.

Before the neck 32 is placed on the body 24, the assembled combinationof the body 24 and the stem 22 can be placed into the medullary canal ofthe reamed out femur by use of a handling tool 108 shown in FIG. 10. Thetool 108 includes a cavity 110, an L-shaped latch 112, and a fin 114that emulate the like features of the neck 32. The stud 30 can thus bereceived in the cavity 110, the L-shaped latch 112 can reside within theL-shaped cavity slot 68, and the fin 114 can slide into the linear slot74.

During use, a first step in attaching the tool 108 to the body 24includes aligning the tool 108 to the body 24 with a trigger 115 (FIG.11) in an unsqueezed or unactuated position. Thus, a simultaneousalignment of the cavity 110 with the stud 30, the latch 112 with theslot 68, and the fin 114 with the slot 74 can be achieved. With theabove elements simultaneously aligned, the tool 108 is advanced onto thebody 24 such that the stud 30 is received in the cavity 110, the latch112 is received in the slot 68, and the fin 114 is received in the slot74. The trigger 115 is then squeezed or otherwise actuated to push aconnecting rod 116 in a direction 118, thereby pivoting the latch 112attached to the rod 116 about a pivot 120. Thus, the distal end of thelatch 112 is hooked or latched into the L-shaped slot 68, as shown inFIG. 10. With the tool 108 thus attached to the body 24, the tool 108can be used to insert the assembled combination of the body 24 and thestem 22 into the reamed out femur.

By using a procedure substantially the reverse of that described above,the tool 108 can also be used to extract the assembled combination ofthe body 24 and the stem 22 from the reamed out femur. Another tool (notshown) is placed in the aligned slot 76 and groove 42 during theextraction process. Further, the tool 108 can also place or extract abroaching apparatus 122 (FIG. 12), which is used in the reamed outfemur.

The proximal end of the broaching apparatus 122 is configured similarlyto the proximal end 54 of the body 24 for connection to the tool 108.More particularly, the broaching apparatus 122 includes a projection124, an L-shaped slot 126, and a linear slot 128 (FIG. 13) for couplingwith the cavity 110, the L-shaped latch 112, and the fin 114,respectively, of the tool 108.

It is also possible, in another embodiment, for the trial body 24 of themodular trial assembly 20 to be provided with serrated teeth, similarlyto the broaching apparatus 122. Thus, the modular trial assembly 20 canfunction both as a trial assembly and as a broaching device.

In another embodiment (FIG. 14) a stem 130 is attachable to a body 132.An unlocking tool 134 unlocks the stem 130 from the body 132 so that thestem 130 can be separated from the body 132.

The stem 130 includes a proximal section 136 and a distal section 138for implantation in a bone. The proximal section 136 includes tworesilient members in the form of opposing tapered prongs 140. The prongs140 are separated by a gap 142. A proximal end 144 of the distal section138 includes a projection or tab 146, best seen in FIG. 15. Each of theprongs 140 includes a latch 148 (FIG. 16) where the surface of the prong140 is perpendicular to a longitudinal axis 150 of the stem 130.

The body 132 includes a through channel 152 having a proximal opening154 at a proximal end 156 of the body 132, and a distal opening 158 at adistal end 160 of the body 132. The width or diameter of the opening 154of the through channel 152 at the distal end 160 is greater than thewidth or diameter of the proximal section 136 of the stem 130, but isless than the width or diameter of the proximal end 144 of the distalsection 138 of the stem 130. The distal end 160 includes a recess orcavity 162 in communication with the through channel 152. The cavity 162is sized to receive the tab 146.

The through channel 152 includes an annular catch 164 where the surfacedefining the through channel 152 is perpendicular to a longitudinal axis166 of the through channel 152. The diameter or width of the throughchannel 152 above, or disposed proximally of, the catch 164 is greaterthan the diameter or width of the through channel 152 below, or disposeddistally of, the catch 164. The proximal end of the body 132 includes anL-shaped slot 168 and a projection 170 for unattached, nonrotatablecoupling to a neck (not shown), as discussed in detail with regard tothe previous embodiment.

During use, thin portions 172 of the prongs 140 are inserted into thedistal opening 158 of the through channel 152. As the prongs 140 move ina proximal direction 174 through the through channel 152, thick portions176 of the prongs 140 engage the wall of the through channel 152, andthe prongs 140 are biased toward each other by the wall of the throughchannel 152. The stem 130 is rotated, if necessary, about its axis 150such that the tab 146 is aligned with the cavity 162 of the body.Farther advancement of the stem 130 in the proximal direction 174results in the tab 146 being received in the cavity 162. The coupling ofthe tab 146 and the cavity 162 prevents the stem 130 from rotating aboutits axis 150 within the through channel 152.

When the latches 148 of the prongs 140 move past the catch 164 of thethrough channel 152 in proximal direction 174, the prongs 140 springoutwardly and are no longer biased by the wall of the through channel152. At this point, the proximal end 144 of the distal section 138engages the distal end 160 of the body 132, thereby limiting furthermovement of the prongs 140 in the proximal direction 174.

If an attempt is now made to move the stem 130 in a distal direction178, opposite to the proximal direction 174, the latches 148 of theprongs 140 latch onto the catch 164 and prevent the prongs 140 frompassing by the catch 164 in the distal direction 178. Thus, the stem 130is locked to the body 132. More particularly, the stem 130 is preventedfrom moving in either of directions 174, 178, and is prevented fromrotating about its axis 150.

The unlocking tool 134 is a hollow, annular device with two openopposite ends 180. In order to unlock the stem 130 from the body 132,one of the ends 180 is inserted through the proximal opening 154 of thethrough channel 152. The open end 180 becomes seated over the thinportions 172 of the prongs 140. Farther movement of the tool 134 in thedistal direction 178 causes the open end 180 to bias the two prongs 140toward one another such that the latches 148 are no longer latched onthe catch 164. The tool 134 can be sized such that the open end 180becomes seated on the catch 164. The stem 130 can then be pulled in thedistal direction 178 by its distal section 138 and can be withdrawn fromthe through channel 152.

In another embodiment (FIG. 17), a body 232 is attached to a stem 230 oftwo-piece construction. That is, the stem 230 has a proximal section 236that is detachable from the distal section 238. The distal section 238includes a bore 280 for receiving the distal end of the proximal section236. The distal section 238 also includes a throughhole 282, best seenin FIGS. 18 and 19, extending through the bore 280. The throughhole 282can be aligned with a throughhole 284 in the distal end of the proximalsection 236 for receiving a pin 286 in each of the throughholes 282,284. Thus, the pin 286 attaches the proximal section 236 and the distalsection 238 of the stem 230.

After the proximal section 236 and the distal section 238 of the stem230 have been attached by insertion of the pin 286, the stem 230 can belocked to the body 232 by the method described above with regard toFIGS. 14-16. Alternatively, it is also possible to insert the proximalsection 236 through a proximal opening 254 of the through channel 252before the proximal section 236 has been attached to the distal section238. That is, the proximal section 236 can be inserted through theproximal opening 254, distal end first, until the latches 248 come torest on or latch onto the catch 262. At this point, a distal end 288 ofthe proximal section 236 extends out of the distal end 258 of the body232. The distal section 238 is coupled to the proximal section 236 byaligning the bore 280 with the distal end 288 of the proximal section236 and receiving the distal end 288 in the bore 280. The pin 286 isinserted through the throughholes 282, 284 in order to attach theproximal section 236 to the distal section 238.

It should be appreciated that the modular trial assembly describedherein is for use during performance of a joint replacement proceduresuch as a hip replacement procedure. Therefore, although the presentinvention is herein described in regard to performance of an exemplaryhip replacement procedure, certain of the concepts of the presentinvention may be utilized in regard to replacement procedures atnumerous other joint locations throughout the body.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, such an illustration and descriptionis to be considered as exemplary and not restrictive in character, itbeing understood that only the preferred embodiment has been shown anddescribed and that all changes and modifications that come within thespirit of the invention are desired to be protected.

There are a plurality of advantages of the present invention arisingfrom the various features of the present invention and associated methoddescribed herein. It will be noted that alternative embodiments of themodular trial assembly and associated method of the present inventionmay not include all of the features described yet still benefit from atleast some of the advantages of such features. Those of ordinary skillin the art may readily devise their own implementations of a modulartrial assembly and associated method that incorporate one or more of thefeatures of the present invention and fall within the spirit and scopeof the present invention as defined by the appended claims.

1. A prosthetic trial for a joint prosthesis, comprising: a bodyincluding a channel having a catch; and a stem including at least oneresilient member configured to be: inserted into said channel in a firstdirection until said at least one resilient member passes by said catch;and latched onto said catch to prevent said resilient member frompassing by said catch in a second direction substantially opposite tosaid first direction, wherein said stem includes a movement-limitingelement configured to engage said body and thereby limit movement ofsaid resilient member in said first direction through said channel,wherein said channel includes a distal opening having a first width at adistal end of said body, said stem including: (i) a proximal sectionconfigured to be inserted into said channel; and (ii) a distal sectionconfigured for implantation in a bone, wherein said movement-limitingelement comprising a proximal end of said distal section of said stem,said proximal end of said distal section of said stem having a secondwidth greater than said first width of said distal opening of saidchannel, said proximal end of said distal section of said stem beingconfigured to engage said distal end of said body.
 2. The trial of claim1, A prosthetic trial for a joint prosthesis, comprising: a bodyincluding a channel having a catch; and a stem including at least oneresilient member configured to be: inserted into said channel in a firstdirection until said at least one resilient member passes by said catch;and latched onto said catch to prevent said resilient member frompassing by said catch in a second direction substantially opposite tosaid first direction, wherein said body includes one of a projection anda cavity, said stem including the other of the projection and thecavity, said projection being configured to be received in said cavityto thereby prevent said stem from rotating about a longitudinal axis ofsaid stem.
 3. A prosthetic trial kit comprising: a stem member includinga proximal portion with at least one resilient member and a distalportion configured for contact with a bone; and a body member defining abore for receiving the proximal portion of the resilient member, thebore including a distal bore portion and a proximal bore portion,wherein the distal bore portion is configured to deform the at least oneresilient member when the at least one resilient member is inserted intothe distal bore portion and the proximal bore portion is configured toprovide less deformation of the at least one resilient member than thedeformation provided by the distal bore portion, and wherein said bodyincludes one of a projection and a cavity, said stem including the otherof the projection and the cavity, said projection being configured to bereceived in said cavity to thereby prevent said stem from rotating abouta longitudinal axis of said stem.
 4. The prosthetic trial kit of claim3, wherein: the body member further defines a catch located between thedistal bore portion and the proximal bore portion; the at least oneresilient member includes a latch, the latch configured to abut thecatch when the at least one resilient member moves from the distal boreportion to the proximal bore portion.
 5. The prosthetic trial kit ofclaim 3, wherein the at least one resilient member comprises: a firstresilient member extending along a longitudinal axis of the stem member;and a second resilient member extending along the longitudinal axis ofthe stem member, and wherein the first resilient member and the secondresilient member define a gap therebetween and the distal bore portionis configured to deform the first resilient member and the secondresilient member toward the longitudinal axis when the first resilientmember and the second resilient member are inserted into the distal boreportion.
 6. The prosthetic trial kit of claim 5, wherein: the bodymember further defines a catch located between the distal bore portionand the proximal bore portion; and the at least one resilient memberincludes a latch, the latch configured to abut the catch along a surfacesubstantially perpendicular to the longitudinal axis when the at leastone resilient member moves from the distal bore portion to the proximalbore portion.
 7. The prosthetic trial kit of claim 5, wherein: thedistal bore portion has a first diameter; and the proximal bore portionhas a second diameter, the second diameter larger than the firstdiameter.
 8. A prosthetic trial kit comprising: a stem member includinga proximal portion with at least one resilient member and a distalportion configured for contact with a bone; and a body member defining abore for receiving the proximal portion of the resilient member, thebore including a distal bore portion and a proximal bore portion,wherein the distal bore portion is configured to deform the at least oneresilient member when the at least one resilient member is inserted intothe distal bore portion and the proximal bore portion is configured toprovide less deformation of the at least one resilient member than thedeformation provided by the distal bore portion, and wherein theproximal bore portion opens to a proximal surface of the body member,the kit further comprising: a delocking member having an outer diameterthat is smaller than the diameter of the proximal bore portion and aninner wall configured to deform the at least one resilient member toabout the same deformation as the distal bore when the delocking memberis inserted into the proximal bore portion and the at least oneresilient member is inserted into the proximal bore portion.
 9. Aprosthetic trial for a joint prosthesis comprising: a body member withan inner wall defining a bore with a longitudinal axis therethrough, acatch located within the bore; a stem member including a distal portionconfigured for insertion into a bone and a proximal portion, theproximal portion configured for insertion within the bore andresiliently deformable to move a latch between a first position and asecond position, such that when the proximal portion is within the boreand the latch is in the first position, the stem is movable along thelongitudinal axis of the bore and when the proximal portion is withinthe bore and the latch is in the second position, the stem is notmovable outwardly from the body member, and wherein said body includesone of a projection and a cavity, said stem including the other of theprojection and the cavity, said projection being configured to bereceived in said cavity to thereby prevent said stem from rotating abouta longitudinal axis of said stem.
 10. The prosthetic trial of claim 9,wherein: a distal portion of the bore has a first diameter; a proximalportion of the bore has a second diameter, the second diameter largerthan the first diameter; the latch is maintained in the first positionby the inner wall when positioned within the distal portion of the bore;and the latch is not maintained in the first position by the inner wallwhen positioned within the proximal portion of the bore.
 11. Theprosthetic trial of claim 10, wherein: the latch comprises a first latchmember located on a first prong of the stem and a second latch memberlocated on a second prong of the stem; and the catch comprises anannular lip.
 12. The prosthetic trial of claim 11, wherein each of thefirst prong and the second prong narrow from a thick distal portion to athin proximal portion.